My procedural volumetric sphere has a tailfin

[scooternva]

The 51m radius sphere that I'm using as the mesh for an OctaneRender volumetric serving as my planetary atmosphere has a "tailfin". It also has hexagonal (or perhaps more accurately, octagonal) banding.

Can anyone please explain what is causing this? Example scene attached... thanks.

It's not supposed to have a tailfin.

[juanjgon]

Why don't you use a spherical volume shape over a null object for this? The leak seems some kind of problem with the geometry, but in any case, if you only need a fog sphere, it is a lot faster to use the sphere shape.

Thanks,
-Juanjo

[scooternva]

Hi Juanjo,

I used a mesh because eventually I’m going to apply an atmosphere to a non-spherical rocky asteroid... taking baby steps to learn all of the quirks by attempting a plain old spherical planet first.

I can work around the tail by just shooting from the other side but it would be nice to know what’s causing this so that it could be fixed altogether. And I still haven’t figured out why those octagonal shapes are showing up... that’s not something I can hide so easily.

thanks...

[juanjgon]

I wonder if this sphere comes from some kind of subdivision that is making it not perfectly spherical. As a volume container, you should use simpler objects with a lot fewer polygons to make the volume building faster. If you have volume artifacts, perhaps you should increase the resolution of the grids, but always working with objects as simple as possible, with few polygons.

Thanks,
-Juanjo

[scooternva]

You have the scene file and *.lwo object file so you can see that this is a tessellated sphere that hasn't been modified at all. I literally created the *.lwo object file by just opening LightWave, creating a ball with tessellation, saved the ball, and exited.

[juanjgon]

I'm investigating the volume data leak outside the mesh. This can be some kind of precision bug, or something like that ...

Thanks,
-Juanjo

[scooternva]

Yeah, it probably is a precision bug. If I up the grid resolution to 125 the tail disappears (but render times go through the roof).